Can't scale two edge loops around the X axis
You have 'Individual Origins' set as your pivot point for transformations in the 3D view header toolbar. At the minute each loop is scaling towards it's individual origin but because the loops have no thickness themselves nothing appears to be happening.

You need 'Median Point' set:



This will find the point in between the two edgeloops in 3d space and use that as the origin for transformations.